Checking for a dirty index or untracked files with Git

The key to reliably “scripting” Git is to use the ‘plumbing’ commands.

The developers take care when changing the plumbing commands to make sure they provide very stable interfaces (i.e. a given combination of repository state, stdin, command line options, arguments, etc. will produce the same output in all versions of Git where the command/option exists). New output variations in plumbing commands can be introduced via new options, but that can not introduce any problems for programs that have already been written against older versions (they would not be using the new options, since they did not exist (or at least were not used) at the time the script was written).

Unfortunately the ‘everyday’ Git commands are the ‘porcelain’ commands, so most Git users may not be familiar with with the plumbing commands. The distinction between porcelain and plumbing command is made in the main git manpage (see subsections titled High-level commands (porcelain) and Low-level commands (plumbing).

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To find out about uncomitted changes, you will likely need git diff-index (compare index (and maybe tracked bits of working tree) against some other treeish (e.g. HEAD)), maybe git diff-files (compare working tree against index), and possibly git ls-files (list files; e.g. list untracked, unignored files).

(Note that in the below commands, HEAD -- is used instead of HEAD because otherwise the command fails if there is a file named HEAD.)

To check whether a repository has staged changes (not yet committed) use this:

git diff-index --quiet --cached HEAD --

• If it exits with 0 then there were no differences (1 means there were differences).

To check whether a working tree has changes that could be staged:

git diff-files --quiet

• The exit code is the same as for git diff-index (0 == no differences; 1 == differences).

To check whether the combination of the index and the tracked files in the working tree have changes with respect to HEAD:

git diff-index --quiet HEAD --

• This is like a combination of the previous two. One prime difference is that it will still report “no differences” if you have a staged change that you have “undone” in the working tree (gone back to the contents that are in HEAD). In this same situation, the two separate commands would both return reports of “differences present”.

You also mentioned untracked files. You might mean “untracked and unignored”, or you might mean just plain “untracked” (including ignored files). Either way, git ls-files is the tool for the job:

For “untracked” (will include ignored files, if present):

git ls-files --others

For “untracked and unignored”:

git ls-files --exclude-standard --others

My first thought is to just check whether these commands have output:

test -z "$(git ls-files --others)"

• If it exits with 0 then there are no untracked files. If it exits with 1 then there are untracked files.

There is a small chance that this will translate abnormal exits from git ls-files into “no untracked files” reports (both result in non-zero exits of the above command). A bit more robust version might look like this:

u="$(git ls-files --others)" && test -z "$u"

• The idea is the same as the previous command, but it allows unexpected errors from git ls-files to propagate out. In this case a non-zero exit could mean “there are untracked files” or it could mean an error occurred. If you want the “error” results combined with the “no untracked files” result instead, use test -n "$u" (where exit of 0 means “some untracked files”, and non-zero means error or “no untracked files”).

Another idea is to use --error-unmatch to cause a non-zero exit when there are no untracked files. This also runs the risk of conflating “no untracked files” (exit 1) with “an error occurred” (exit non-zero, but probably 128). But checking for 0 vs. 1 vs. non-zero exit codes is probably fairly robust:

git ls-files --others --error-unmatch . >/dev/null 2>&1; ec=$?
if test "$ec" = 0; then
    echo some untracked files
elif test "$ec" = 1; then
    echo no untracked files
else
    echo error from ls-files
fi

Any of the above git ls-files examples can take --exclude-standard if you want to consider only untracked and unignored files.